Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 251025

Area Forecast Discussion
National Weather Service Lincoln IL
525 AM CDT Tue Apr 25 2017

.SHORT TERM...(Today and tonight)
ISSUED AT 219 AM CDT Tue Apr 25 2017

Still quite a bit of dry air over the forecast area early this
morning, with 2 am dew points in the 30s along and west of I-55.
However, dew points in the 50s have pushed as far north as central
Indiana, and will spread westward with time through the day. With
temperatures a couple degrees warmer than yesterday -- generally
around 80 degrees -- the added moisture will become a bit more

Latest surface map showing low pressure over north central Iowa,
with a frontal boundary extending southwest to another low over
the Oklahoma panhandle. As this southern low rides northeast
today, the warm front will surge northward, and much of the rain
will be on the northern flank. However, showers and thunderstorms
will be developing along the trailing cold front this evening. ARW
model has a line of storms moving into the northwest CWA as early
as late evening, but other higher resolution models are more
focusing on Missouri with a brush-by over western Illinois after
midnight. Have included chance PoP`s as far east as Springfield
and Lincoln overnight.

.LONG TERM...(Wednesday through Monday)
ISSUED AT 219 AM CDT Tue Apr 25 2017

Lots to focus on during this part of the forecast, in terms of
severe weather potential and heavier rainfall.

Latest SPC Day1 outlook introduced a slight risk of severe weather
over most areas west of I-57 on Wednesday. Most models have the
cold front moving into the western CWA during the afternoon hours,
when 0-6km bulk shear is over 50 knots and MUCAPE`s reach the
1500-2000 J/kg range. High-res models are a bit variable with the
timing, with the ARW fastest (along I-57 by sunset) and the
NAM slowest (still west of the Mississippi River at the same
time). Highest PoP`s during the afternoon will be west of I-55 and
80-90% PoP`s arrive early evening. In terms of timing of the rain
end, the GFS has a fairly clean back edge, but most models linger
some showers through the night as the upper trough arrives, so
have only scaled back to around 50% over the far western CWA after
midnight and lingered some rain over the east into Thursday
morning. With precipitable water (PWAT) values around 1.5 to 1.7
inches Wednesday into Wednesday evening, some heavier rains are
likely mainly focused along the I-55 corridor.

Late week storm system remains a challenge. Evening model guidance
continues to dig a broad upper trough over the Rockies, closing
off a low near the 4-corners region by late Friday evening. Some
better agreement is being seen with this low lifting into the
central Plains, with the surface cyclone tracking across northwest
Illinois early Sunday. While a warm front sets up shop over
central Illinois, the speed of it lifting north is more uncertain,
with the GFS over the northern CWA by late Saturday afternoon and
the ECMWF about 12 hours slower with that position. However, the
heavy rain aspect is in better agreement, with an extended period
of 1.50+ inch PWAT`s from late Friday night into midday Sunday.
Widespread soaking rains are likely this weekend, which may start
to cause some impacts with time.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 525 AM CDT Tue Apr 25 2017

Main concern will be with the winds, as VFR conditions continue to
prevail. Southerly winds expected to increase by mid to late
morning and gust to around 25 knots. By mid evening, the stronger
gusts will drop off, but winds will still average about 10 knots.
Lowering of ceilings will begin this evening, but will remain quite
high; by the end of the period, ceilings will only be down to
around 5,000 feet.


Issued at 400 AM CDT Tue Apr 25 2017

Latest guidance showing 10-hour dead fuel values of 5-6% across
much of the northwest half of the forecast area. Dew points over
that area overnight have not recovered much and were still largely
in the 30s as of 3 am. While some improvement in dew point is
expected today, strong southerly winds will push temperatures to
around 80 degrees this afternoon with minimum relative humidity
values around 30%. Conditions not quite at red flag level, but
wind gusts to around 30 mph will raise some concern.




SHORT TERM...Geelhart
LONG TERM...Geelhart
FIRE WEATHER...Geelhart is the U.S. government's official web portal to all federal, state and local government web resources and services.